Squeeze harder

After four rounds of U.N. sanctions against Iran, followed by ever more stringent U.S. and European Union measures, Tehran is suffering some economic pain for refusing to curb its nuclear ambitions. Finally.

The good news:

•Gasoline imports to Iran reportedly fell by half in July compared with May levels, according to the International Energy Agency. Iran must import a sizable chunk of its fuel and it is paying a huge premium for that gasoline, when it can find suppliers.

•More companies — not just energy firms — are turning their backs on Tehran. Toyota said last week that it has suspended auto exports to Iran.

•Tehran has scaled back its ambitions to become a major liquefied natural gas exporter, The Wall Street Journal recently reported. That's probably because the country is having trouble acquiring Western technology.

•Banks and insurance companies are paying heed. The evidence: International investment in Iran's oil and gas developments is drying up.

The bad news: So far all of this economic pain has not compelled Iran to halt its nuclear program.

One major reason: Tehran's chief enablers, the Russians and Chinese.

The Chinese voted for sanctions but still sell gasoline to Tehran. The Russians voted for sanctions, but announced last week that they would begin loading nuclear fuel into Iran's first nuclear power plant by Saturday.

What terrible timing. For years, the Russians dragged their feet and invented excuses not to flip the switch on Iran's power plant. Now they cave, just when international economic sanctions are starting to bite?

A crisis is a terrible thing to waste, Mr. Putin.

The Iranians already have enough nuclear material for two bombs, with further enrichment. Analysts at the Institute for Science and International Security recently raised the possibility that Iran could be conducting a "slow motion breakout." Instead of a sudden leap into the nuclear club, the Iranians are gradually gaining expertise in enriching fuel and building the bomb.

How to stop Tehran? "It may be that their ideological commitment to nuclear weapons is such that they're not making a simple cost-benefit analysis on this issue," President Obama said recently. Or it may be that the costs are not yet high enough to force Iran to back off.

Let's find out.

Expand U.S. sanctions against international companies doing business with the Iranian Revolutionary Guards, the power behind the mullahs and the regime's enforcers. That needs to go beyond banks and energy firms to include all foreign companies with commercial ties to the Guards.

Aggressively enforce the new sanctions against companies that supply Iran's energy sector. Where to start? The Foundation for Defense of Democracies recently issued a target list of 18 big companies still dealing with Iran. Those include major Russian and Chinese companies that do business in the U.S. and Iran.

Realistically, no, we don't have overwhelming leverage against the Russians and Chinese. But let's remind those leaders that helping Iran evade sanctions hikes the chances of two disastrous outcomes: a military strike against Iran's nuclear facilities or a Middle East nuclear arms race.